The concept itself isn't bad; I think logistically you might run into issues. The way you described it, if you have 72 hours from the start of an auction to the end of it, one of 2 things is going to happen. If no other auctions occur during that time period, you're staring at a 5 month draft. If you have other auctions taking place, you could run into issues of illegal bids if owners aren't careful (not keeping track of their bids, which shouldn't be that difficult if 16 players are out at a time but when you multiply is by 2 or 3 it could get tricky) and you'll have a lot going on at once. You'd probably be staring at about as much work as I had to do for the completely open draft.
The concept would work if you either had multpile batches running at once (again, just make sure you can keep everything straight) or you'd have to cut the time down of the auctions from start to finish.
I hope you don't look at this as me being negative or nitpicky- I'm really just trying to help. I figure if I can help you avoid some of the mistakes we made, you won't make them. If I can point out a potential flaw and we can come up with a good solution, it's one less thing to possibly go wrong. Based on experience, I believe you really need to have everything lined up for an auction draft.